Accounting for Transfers and Servicing of Financial Assets and Variable Interest Entities - Additional Information (Detail) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2020		Mar. 31, 2019	Dec. 31, 2019
Variable Interest Entity [Line Items]
Assets related to consolidated VIEs		$ 542,909			$ 495,426
Liabilities related to consolidated VIEs		490,747			442,943
Available-for-sale securities	[1]	123,681	[2]		122,613
Minimum [Member]
Variable Interest Entity [Line Items]
Aggregate amount of investments in unconsolidated VIEs		1			1
Maximum [Member]
Variable Interest Entity [Line Items]
Aggregate amount of investments in unconsolidated VIEs		86			87
Financial Support Waived Fees [Member]
Variable Interest Entity [Line Items]
Financial or other support to money market funds		8		$ 7
Private Investment Funds and Partnerships [Member]
Variable Interest Entity [Line Items]
Investment carrying amount		34			31
Maximum exposure to loss		56			55
Community Development and Tax Advantaged Investments [Member]
Variable Interest Entity [Line Items]
Federal and state income tax credits recognized in tax expense		150		145
Expense related to investments		142		132
Investment tax credits		99		84
Expenses related to investments recognized in tax expense		101		$ 81
Investment carrying amount		6,147			6,148
Maximum exposure to loss		12,453			12,118
Community Development and Tax Advantaged Investments [Member] | Variable Interest Entity [Member]
Variable Interest Entity [Line Items]
Assets related to consolidated VIEs		3,700			4,000
Liabilities related to consolidated VIEs		2,900			3,200
Conduit [Member]
Variable Interest Entity [Line Items]
Available-for-sale securities		13			12
Tender Option Bond Program [Member] | Variable Interest Entity [Member]
Variable Interest Entity [Line Items]
Assets related to consolidated VIEs		3,100			3,000
Liabilities related to consolidated VIEs		$ 1,600			$ 2,700

[1] Includes only collateral pledged by the Company where counterparties have the right to sell or pledge the collateral.

[2] The weighted-average maturity of total available-for-sale investment securities was 4.2 years at December 31, 2019, with a corresponding weighted-average yield of 2.38 percent.